1. Field of the Invention
The present invention relates to a horizontal scanning pulse signal control circuit used in a multi-scan type display apparatus adapted to a plurality of different scanning frequencies.
2. Description of the Related Art
A prior art horizontal scanning pulse signal control circuit is constructed by a delay circuit for receiving a horizontal synchronization signal to generate a delayed pulse signal in accordance with a horizontal position control voltage signal, a saw-tooth wave generation circuit which generates a saw-tooth wave signal, a comparator for comparing the saw-tooth wave signal with a pulse width selection voltage, and an AND circuit, connected to the comparator and the delay circuit, for generating a horizontal scanning pulse signal. This will be explained later in detail.
In the above-described prior art horizontal scanning pulse signal control circuit, however, the inclination of the saw-tooth wave signal is directly affected by the variations in the performances of the various elements of the saw-tooth wave generation circuit including capacitors and resistors to vary the pulse width of the horizontal scanning pulse signal and hence adversely affect the dimensions of the image displayed on the screen.